Recycling of solid oxide electrolyzer stacks

In recent years, hydrogen has become an increasingly important energy carrier, replacing fossil fuels. In this context, electrolyzers have become a focal point of global research, as they facilitate the production of green hydrogen. Among electrolyzers, solid oxide electrolyzers are one of the most widely researched due to their high efficiency and their variability in terms of fuels and operation as fuel cells. However, due to the use of critical materials in combined with a relatively short operational lifespan, the development of recycling strategies is becoming increasingly crucial if these electrolyzers are to become a sustainable option for green hydrogen production. This study proposes the first comprehensive recycling scheme for solid oxide electrolyzer stacks. Data on the materials used by electrolyzer manufacturers from around the world was compiled and compared. Based on these materials, published recycling approaches from dismantling, mechanical recycling and metallurgy were combined with additional studies to develop a holistic recycling process aimed at recovering critical raw materials. Options for closed-loop and open-loop reuse were considered and existing gaps and challenges were identified. The current status of recycling solid oxide electrolyzer stacks demonstrates that the principle is feasible and that a significant proportion of the materials used can already be separated and recovered. However, existing gaps, such as the separation of the nickel mesh from interconnects and the separation of various oxygen ion conductors, currently result in materials being downcycled or recycled in an open loop.